ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ The first step beyond stand-alone machines still place the processing power on a single host computer but distributed input/output (I/O) functions out to user sites.

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ It placed these functions in dumb terminals which sent user keystrokes to the host an painted host information on the terminal screen but did little else

Challenges

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ Computer was often overloaded by the need to process both applications and terminal communication

And this resulted in slow response times

.

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ Resulted in high transmission cost. All keystrokes had to be sent to the host computer for processing

Generated a great deal of traffic.

To reduce transmission costs, most terminals limited the information they could display to monochrome text (one color against a contrasting background) graphics were seldom available

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ These advances extended the life of terminal-host systems, even these advanced IBM systems were less satisfactory than subsequent developments, including the client/serve systems described next.

Client/Server Systems

After terminal hosts systems

A big breakthrough came in form of client/server systems

They placed some power on the client computer

This was made possible by the emerge of personal computers in the 1980

File Server Program Access

The server's only role is to store programs and data files.

For processing the program is copied across the network the to the client PC along with data files

The client PC does the actual processing of the program and data files

Many client Pc's are operatively underpowered

Even the faster are usually fairly slow compared to servers

File server program access is only sufficient for word processing, email and other small application

It is not useful for large database applications.

Client/Server processing

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ In contrast in full client/server processing the work is done by programs on two machines

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ retrieve though desired file from memory and create an HTTP response message that contains the requested file or a reason why it can not be delivered

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ MIME is a standard for describing diffent types of file formats , so that the receiver will know how to process the file delivered in an HTTP response message (or an e-mail attachment

Central Control ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ Can be problem form the end users point of view.

Limits what end users can do

Peer-to-Peer Applications

User PCs communicate directly with one another at least for part of their work

All of the work involves P2P interactions.

2 user computers work without the assistance of a central server and also without its control

BENEFITS

Client users are freed fro central control for better or worse network traffic is spread more evenly and less user computer capacity is wasted

Problems

Transient Presences ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ Another problem is that each time a user PC uses the Intent its DHCP server is likely to assign it a different IP address

No permanent phone numbers or IP address on the server

Security

Without centralized filtering on servers security will have to be implemented on all user PCs, or chaos will result

Pure peer-to-peer applications: Gnutella

Viral networking for searches

Gnutella

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ Gnutella is a pure P2P file-sharing application that addresses the problems of transient presence and transient IP addresses without resorting to the use of any server.

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ The user's PC connects to one or a few other user PCs

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ Which each connect to several other user PCs and so forth

ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ ÃÂÃ Subsequent search queries sent b the user also are passed virally to all computers reachable within a few hops

Direct File downloads

Actual file downloads are done using strictly peer-to-peer communication between the user's PC and the PC holding the file to be downloaded. There is no viral networking in actual file downloads

Super Clients

Gnutella cheats

It relies on the presence of many super clients that are always on

That have fixed IP address that have many files to share and that are each connected to several other super clients

They are not precisely servers

Using Servers to Facilitate P2P interactions

Most p2p do not even try for a pure P2P approach

Rather they use facilitating servers to solve certain problems in P2P interactions but allow clients to engage in P2P communicating for most of the work.

Napster

Used an index server

When stations connect to napster they first upload a list of files available for sharing to an index server

Later when they search, their searches go to the index servers and are returned form there

Once a client receives a search response it selects a client who has the desired file and contacts that client directly.

The large file transfer usually on to five megabytes is done entirely peep-to-peer.

H.323

In videoconferencing and IP telephony communication is governed by the H.323 standard.

The calling party knows the called party's IP address it can connect to the called party directly.

The communicating typically uses gatekeeper servers

The called party s gatekeeper authenticates the caller and then facilitates the connection to the called party

If there is a gatekeeper in a terminal's zone, the terminal is required to use the gatekeeper to communicate

Another type of server, a gateway connects and IP network to the Public Switched Telephone Network.

If all communication goes through the gatekeeper after the initial connection is made, additional services are possible, such as call waiting etc.

This spectrum of capabilities illustrates the type of flexibility that would be desired able in other P2P programs to allow individual firms to select the degree of client-server versus P2P functionality that would be best for their organization.

Processor Utilization:

SETI@HOME

PC processors sit idle most of the time

This is even true much of the time when a person is working at their keyboard. This is especially true when the user is a way form the computer doing something else.

One example of employing P2P processing to use this wasted capacity is SETI@HOME

When the computer is idle the screen saver awakens asks the SETI@home server for work to do and then processes the data.

Processing ends when the user begins to work which automatically turns off the screen saver ,

The future of P2p

it is so new that it is impossible to forecast its future with any certainty when should note that many more p2p applications are likely to appear in the near future offering a much broader spectrum of services than we have seen here

GAINING PERSPECITVE

Market realities

There will be one bullion intent users by 2005

Europe and Asia-pacific region will vie to have the largest number of intent users

United states is third place

The United States is expected to account for 36 percent of e-commerce revenues

Citation styles:

Networked Applications, Notes from Business Data Communication CSI120, describes applications used for networking ther functions, benefits, and how they work. (download document for ease of reading). (2004, December 10). In WriteWork.com. Retrieved 16:01, December 09, 2016, from http://www.writework.com/essay/networked-applications-notes-business-data-communication-c

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